The present invention relates to ultrasonically energized scalpel blades and particularly to blades having improved configurations for cutting and coagulating tissue.
In my prior application Ser. No. 07/771,182, filed Oct. 4, 1991, the disclosure of which is incorporated herein by reference, an ultrasonic surgical instrument is disclosed which includes an ultrasonic energy source in a handpiece ultrasonically coupled through an extension to a surgical tool, e.g., a surgical blade, at the tip of the blade extension whereby ultrasonic energy is transmitted from the ultrasonic energy source to the surgical blade and coupled with the tissue to which the blade is applied. That ultrasonic surgical blade achieved exceptional coagulation while cutting by reducing the sharpness and, consequently, increasing the dullness or bluntness of the blade, in comparison with standard sharp surgical blades. Prior to the discovery set forth in that application, it was believed that the same sharp blades used in hand-held surgical scalpels should be applied to ultrasonic surgical scalpels. It was discovered, however, that an otherwise dull blade, when coupled ultrasonically to tissue, enhances the sharpness of the blade when applied to incise and dissect, while simultaneously effecting coagulation. Generally, sharp blades pass through the tissue with less force and less tissue coupling and hence produce less coagulation. Thus, to achieve tissue coagulation and hemostasis, ultrasonic scalpel blades need not be as sharp as standard scalpel blades. In that prior application, the relationship between the type of tissue cut and the sharpness or dullness of the blade is set forth.
It has been found, however, that dull blades do not cut particularly well through relatively loose and unsupported tissues, such as fat unless the tissues are supported against a hard surface (to afford effective cutting with simultaneous coagulation). It has been discovered that an ultrasonic blade having a hook portion and formed sufficiently dull can provide both superior coagulation and effective cutting of loose and unsupported tissue. The hook portion of the ultrasonic blade engages the tissue as the blade is drawn along the tissue and allows the blade to grasp and tension the tissue (hence supporting the tissue) to enhance the cutting action. By stretching or tensioning the tissue, the otherwise dull blade is able to effectively cut as well as coagulate relatively loose and unsupported tissue. Consequently, with an ultrasonic blade having a hook portion, a blade may be selected in accordance with its dullness depending upon the type of surgery with the assurance that simultaneous effective cutting and coagulation can be achieved. For example, where it is necessary to afford greater hemostasis, i.e., where a patient will bleed substantially, as in a gall bladder operation, a very dull ultrasonic blade with a hook is preferable. With such a dull hook blade, effective cutting action is achieved and, when greater power is applied, the coupling with the loose and unsupported tissue provides exceptional hemostasis. Even large blood vessels up to 3 millimeters have been hooked and coagulated while being severed. Fat and parenchymous tissue can be cut by ultrasonically activated dissection blades having hook portions that are approximately 25/1000 inches thick with no blade edge. Connective tissues can be cut by blades with hook portions 25/1000 inches thick and having a 60.degree. blade edge or no edge at all. Generally, the hook portion may be sharpened to angles between 30.degree. and 70.degree.. Such dissection blades provide exceptional hemostasis for good cutting, even in fibrous elastic tissues.
It has also been found according to the present invention that the ultrasonic motion is greatest at the tip of the blade and that the surface area at the tip is proportional to the amount of energy that is coupled to the tissues for coagulation. The large surface area facilitates application of adequate pressure to optimize coupling of the ultrasonic energy with the tissue. Consequently, in accordance with the present invention, blades with flat, non-pointed and non-sharpened tips are provided and have proven highly effective for coagulation of bleeders. Such tips penetrate tissues less during coagulation of bleeders than sharpened tips. Flat tips also provide cavitation fragmentation of tissues to facilitate dissection of loose, low density tissues.
Several specific embodiments of blades employing the principles of the present invention are disclosed. In one such blade principally useful in laparoscopic surgery, e.g., gall bladder surgery, there is provided a blade body having a shank, side faces, a tip opposite the shank and side edges extending from the shank to the tip. At least a side edge of the blade and the tip, are unsharpened and are flat. One of the side edges, however, is provided with a recess which defines with the tip a hook between the one side edge and the tip for grasping and tensioning tissue as the blade is drawn along the tissue. With the flat edge of the blade bearing against tissue, the maximum amount of energy is transferred into the tissue, rendering the blade effective to coagulate bleeders. Simultaneously, the hooked portion of the blade grasps and tensions the loose, unsupported tissue to facilitate the cutting action of the blade through the tissue.
In one specific form of the invention, the blade is in the general shape of a spoon. One side edge of the blade, however, has an arcuate recess. That is, an opposite side edge and tip form a continuous convex curve about the periphery of the blade, while the one side edge defining the hooked portion characterized by a concave curve. All of the edges may be flat and unsharpened. Alternatively, the concave surface may be sharpened with an edge angle, preferably from 30.degree. to 70.degree. depending upon the nature of the surgery. This sharpened hook design enables the blade to dissect even unsupported tissues providing effective coagulation of bleeders and exceptional hemostasis. The generally round shape facilitates application to various tissue contours from a single point of entry and helps prevent puncture during coagulation when substantial pressure is applied to couple the ultrasonic energy with the tissues.
In another form of the present invention, there is provided a hooked dissection blade which is for general purpose use rather than specific use, for example, for laparoscopic surgery. In this form of blade, the blade body is essentially planar, having a recessed portion along one, preferably non-sharpened, side edge to form a hook portion with the tip of the blade. A linearly extending portion of the opposite side edge is sharpened, preferably within a range of 25.degree. to 45.degree.. The tip of the blade is flat and extends linearly between the opposite side edges for maximum energy transfer to the tissue during use. Thus, both the linearly extending flat tip and the single straight cutting edge optimizes the coupling of the ultrasonic energy to the tissue to provide exceptional coagulation and hemostasis while the hook portion tensions unsupported tissue to enhance the cutting action.
In both blades specifically described above, i.e., a spoon-shaped hooked blade for laparoscopic surgery and a hooked dissector blade for general purpose, the blade is carried by a blade coupler which has a stepped horn for amplifying the ultrasonic energy transmitted along the blade coupler to the blade. The blade coupler thus steps from one diameter to a reduced diameter, with consequent amplification of the vibratory axial motion. In the blades hereof, the stepped amplifying horn, however, has a radius which reduces the extent of amplification of the axial vibratory motion to preclude the blade from breaking through fatigue. It will be appreciated that it is important that the stepped horn not lie in the vicinity of a node, i.e., a point of minimal or no axial vibratory motion along the blade coupler. Additionally, in the laparoscopic blade hereof, the node is preferably located in the reduced diameter shank of the blade coupler, whereas in the hooked dissector, the node is located in the larger diameter portion of the coupler. In both cases, of course, the nodes cannot lie in any transition area, i.e., at the stepped horn or at the connection between the blade coupler and either the power element or an extension used for laparoscopic surgery. Also, it will be appreciated that the anti-nodes, i.e., the points along the coupler of maximum energy, are located at the connecting point between the blade coupler and either the power element or extension, as applicable, and the tip of the blade.
In a preferred embodiment according to the present invention, there is provided an ultrasonic scalpel blade for an ultrasonic scalpel comprising a blade coupler having a blade body and a shank extending from the blade body for coupling with a source of ultrasonic energy and transmitting the energy to the blade body, the body having side edges and a tip opposite the shank, one of the side edges having a recess formed therein and defining a hook portion between the one side edge and the tip for tensioning tissue as the blade is displaced along the tissue, thereby facilitating cutting and coagulation of the tissue upon application of ultrasonic energy to the tissue.
In a further preferred embodiment according to the present invention, there is provided an ultrasonic scalpel blade for an ultrasonic scalpel comprising a blade coupler having a blade body and a shank extending from the blade body for coupling with a source of ultrasonic energy and transmitting the energy to the blade body, the body having side faces, side edges and a tip opposite the shank, at least one of the side edges having non-sharpened flat edge surfaces extending linearly between opposite side faces of the blade and in a direction generally normal to the side faces to facilitate coagulation of the tissue upon application of ultrasonic energy to the blade and ultrasonically coupling the blade and tissue as the blade is displaced along the tissue.
In a still further preferred embodiment according to the present invention, there is provided a method of incising and coagulating tissue comprising the steps of providing an ultrasonically actuated scalpel blade having side edges, a tip at an end of the blade and a hook along one of the side edges, and simultaneously cutting and coagulating tissue by (i) applying the ultrasonically energized scalpel blade to the tissue and (ii) tensioning the tissue by engaging the tissue with the blade hook as the blade is drawn along the tissue.
Accordingly, it is a primary object of the present invention to provide novel and improved ultrasonic actuated scalpel blades having improved cutting and coagulating characteristics, particularly for use in soft, relatively loose, unsupported tissue.
These and further objects and advantages of the present invention will become more apparent upon reference to the following specification, appended claims and drawings.